This invention is related to a system for providing auxiliary electrical power for a motor vehicle such as a heavy-duty truck. Specifically, the system provides energy by converting thermal exhaust gas energy to electrical power.
Improving the energy efficiency of motor vehicles is of primary importance to vehicle manufacturers and operators. These objectives are particularly important for heavy-duty trucks for which fuel cost is a significant component of overall operating cost and therefore the cost for delivering payloads to remote destinations. Presently, auxiliary electrical loads to operate systems on board a heavy truck including interior and exterior lighting, air conditioning, heating, engine control system, and other accessories. These demands constitute a significant load on the vehicle engine. Shaft horsepower must be taken from the engine and converting to electrical energy, typically through a belt driven alternator to provide an electrical power source for such auxiliary loads. The onboard DC battery provides cranking energy for starting the vehicle engine and further acts as a buffer to accommodate differences between available electrical energy from the alternator and the instantaneous electrical demand. At the same time that power is being taken from the engine to drive the alternator, considerable energy is dispersed to the atmosphere in the form of hot engine exhaust gases. The discharge of heated gases represents a thermal efficiency penalty for the overall motor vehicle system.
In accordance with this invention, waste thermal energy from a motor vehicle in the form of hot exhaust gases is used to provide a heat source for a Stirling engine which converts heat input energy into mechanical shaft output power, which drives an electrical alternator. If desired, a small combustion furnace can be associated with the Stirling engine to provide electrical output from the alternator in conditions such as start up where sufficient heat energy is not available from the engine exhaust gases to power the Stirling engine.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which the present invention relates from the subsequent description of the preferred embodiment and the appended claims, taken in conjunction with the accompanying drawings.